Robert C. Murtha Jr. has made a sizable living for years working with companies that rely on Pentagon contracts over which his uncle, Rep. John P. Murtha (D-Pa.), holds considerable sway.

He has maintained that his uncle played no role in his defense-related work, much of it secured without competition. Newly obtained documents, however, show Robert Murtha mentioning his influential family connection as leverage in his business dealings and holding unusual power with the military. The documents add to mounting questions about Rep. Murtha, whose use of federal earmarks to help favored defense companies and whose relationship with a former lobbying firm are under scrutiny by federal investigators.

The congressman has used his control over Pentagon funds to build a hub of defense-related industry in his congressional district and has also received generous campaign donations from the companies.

Robert Murtha, an engineer, benefited from some of the defense contracts when companies brought him in to manage a small portion of the work. Even when the main contract shifted to a new company, he continued to be paid as part of the team. Some former business associates and employees told The Washington Post that they thought the role played by Robert Murtha's companies was unnecessary.

Jeff Curtis, an engineer who worked for Robert Murtha's company in 2001, contacted The Post to say that he and some co-workers did virtually no work on a project to make kits to test for biological agents. Curtis said he remains "furious" that taxpayer dollars were wasted.

"I was always thinking, 'Why is the government paying this company?' " said Curtis, 29, who is now doing engineering work in North Carolina. "If it's fair to have this kind of no-bid work, I'll start a company and do it for half as much. Because this company didn't do anything."

In e-mails obtained by The Post, Robert Murtha told a business partner in 2001 that there were conditions for "keeping funds flowing." Part of the federal work, he said, must be channeled to Johnstown, Pa., his uncle's home town.

"This has been a requirement for what I do to get dollars through," Robert Murtha wrote in an e-mail to a senior official with NMS Imaging of Silver Spring, the lead contractor on a project to produce biological test kits.

Robert Murtha, 49, recently told The Post that it is "unfortunate" that some will assume his family ties led to government contracts.

"We do good work," he said.

He did not respond to requests for comments on his e-mails or operations. Rep. Murtha's office requested written questions but did not respond to them.

The documents obtained by The Post, including Robert Murtha's e-mails and invoices, appear to contradict his assertions that his uncle played no role in his extensive Pentagon business.

He warned in an e-mail that failing to move work to Johnstown could jeopardize "financial rewards" for all parties. "Everyone on your side and on my side benefit from this, without having invested anything," he wrote.

Robert Murtha has worked on military projects since the late 1990s. In recent years, his company, Murtech, earned about $4 million a year from the Pentagon on contracts without competition, including for storage at a Glen Burnie warehouse.

Rep. Murtha, the powerful chairman of the House Appropriations defense subcommittee, has repeatedly defended his efforts to bring defense jobs to the economically depressed Johnstown area.

The documents obtained by The Post date to 1999, as the Pentagon purchased more equipment to protect soldiers from biological and chemical weapons, a move Rep. Murtha strongly backed.

The defense giant Lockheed Martin won an early contract to create handheld field kits to detect agents such as anthrax and ricin. The kits, resembling drugstore pregnancy tests, featured biological detection material sealed in a plastic strip.

For logistics support, Lockheed subcontracted to Betac, a defense firm working on weapon-detection systems, where Robert Murtha worked.

The contract shifted to three companies over the years, but Robert Murtha moved with it. And at times he gave associates the impression that he controlled the entire contract, according to interviews and documents.

In 1999, the prime contract shifted from Lockheed to NMS Imaging. NMS subcontracted its logistics work to Arlington-based ACS Defense. Robert Murtha left Betac to become an ACS vice president.

Although he worked for a subcontractor, Robert Murtha sometimes called the shots on larger decisions, documents and interviews show. In 2000, he began demanding that NMS move some of its assembly work to Johnstown, records show. NMS officials complained at first but eventually complied.

Robert Murtha repeatedly warned NMS and others that the Pentagon generally deferred to his judgment, documents show.

"These projects are given to us because of my technical and performance reputation," he wrote in 2001. "When I let things go a certain way, it is normally accepted."

The invoices provided to The Post show that the Pentagon's contracting official on the project, David Cullin, authorized payments to ACS Defense and simultaneously to Murtech, then a small consulting firm owned by Robert Murtha. In October 2000, NMS questioned a Murtech invoice and whether Cullin approved billings for what appeared to be duplicative supplies and services. In response, Cullin wrote to NMS, "Please expedite as much as possible," regarding an $18,000 payment to Murtech.

ACS spokesman Ken Ericson said he could not explain Murtech's billings but said ACS will look into them.

Reached by telephone, Cullin said he saw no evidence of wasteful project spending and did not recall approving Murtech's payments.

"I know Bob Murtha," Cullin said. "I found him in my time to be a very honorable man who's done very professional work in everything he has done."

NMS lost the test-kit contract in 2003, and a contract worth up to $200 million shifted to S.A. Scientific of San Antonio. That year, Murtech became a subcontractor.

Cullin is now a senior vice president of ICX Technologies; that company has used as its lobbyists the PMA Group, the former firm now under scrutiny for its ties to the congressman. Last year, ICX won a contract worth up to $700 million to develop biological test kits and protective gear. Murtech was brought in as a subcontractor.